Re: [PATCH v3 03/13] mm/debug_vm_pgtable/ppc64: Avoid setting top bits in radom value

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On 9/1/20 8:45 AM, Anshuman Khandual wrote:


On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
ppc64 use bit 62 to indicate a pte entry (_PAGE_PTE). Avoid setting that bit in
random value.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
  mm/debug_vm_pgtable.c | 13 ++++++++++---
  1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 086309fb9b6f..bbf9df0e64c6 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -44,10 +44,17 @@
   * entry type. But these bits might affect the ability to clear entries with
   * pxx_clear() because of how dynamic page table folding works on s390. So
   * while loading up the entries do not change the lower 4 bits. It does not
- * have affect any other platform.
+ * have affect any other platform. Also avoid the 62nd bit on ppc64 that is
+ * used to mark a pte entry.
   */
-#define S390_MASK_BITS	4
-#define RANDOM_ORVALUE	GENMASK(BITS_PER_LONG - 1, S390_MASK_BITS)
+#define S390_SKIP_MASK		GENMASK(3, 0)
+#ifdef CONFIG_PPC_BOOK3S_64
+#define PPC64_SKIP_MASK		GENMASK(62, 62)
+#else
+#define PPC64_SKIP_MASK		0x0
+#endif

Please drop the #ifdef CONFIG_PPC_BOOK3S_64 here. We already accommodate skip
bits for a s390 platform requirement and can also do so for ppc64 as well. As
mentioned before, please avoid adding any platform specific constructs in the
test.



that is needed so that it can be built on 32 bit architectures.I did face build errors with arch-linux

+#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
+#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
  #define RANDOM_NZVALUE	GENMASK(7, 0)

Please fix the alignments here. Feel free to consider following changes after
this patch.

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 122416464e0f..f969031152bb 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -48,14 +48,11 @@
   * have affect any other platform. Also avoid the 62nd bit on ppc64 that is
   * used to mark a pte entry.
   */
-#define S390_SKIP_MASK         GENMASK(3, 0)
-#ifdef CONFIG_PPC_BOOK3S_64
-#define PPC64_SKIP_MASK                GENMASK(62, 62)
-#else
-#define PPC64_SKIP_MASK                0x0
-#endif
-#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
-#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
+#define S390_SKIP_MASK GENMASK(3, 0)
+#define PPC64_SKIP_MASK        GENMASK(62, 62)
+#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
+#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
+
  #define RANDOM_NZVALUE GENMASK(7, 0)
static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot)


Besides, there is also one checkpatch.pl warning here.

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#7:
ppc64 use bit 62 to indicate a pte entry (_PAGE_PTE). Avoid setting that bit in

total: 0 errors, 1 warnings, 20 lines checked



These warnings are not valid. They are mostly long lines (upto 100) . or some details mentioned in the () as above.

-aneesh



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